Nevertheless, and despite the small sample size of our study, plausible signals of positive selection were detectable in DFT1 and DFT2, and it is likely that these are operating to increase fitness of cells within tumours (e.g. PDGFRB and PDGFRA amplification in DFT1 and DFT2, respectively, and MGA loss-of-function in DFT1) and to enhance transmission potential (e.g. chromosome Y loss in DFT2). This evidence concerns the gene PDGFRB and neoplasm.